Magnetic brush roll having resilient polymeric surface

ABSTRACT

A magnetic brush roll of an electrostatic reproduction machine is formed of a non-magnetic core with a resilient polymeric material such as polyurethane, for example, on its surface. The polyurethane surface is textured to provide a desired roughness, is non-abrasive, and is abrasion resistant. Carbon is added to the polyurethane to render it conductive.

United States Patent 11 1 Buckley et al.

[ 1 Feb. 4, 1975 1 1 MAGNETIC BRUSH ROLL HAVING RESILIENT POLYMERICSURFACE [75] Inventors: Lawrence Webb Buckley; Raymond Alex Daniels,both of Lexington; James Dewayne Froula, Versailles; Arthur Holt Knight,Frankfort, all of Ky.; Dale Clifiton Stapleton, Boulder, Colo.; GeorgeThomas Williams, Georgetown, Ky.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: Jan. 7, 1974 [21] Appl. No.: 131,275

[52] U.S. C1 118/637, 117/175, 355/3 DD [51] Int. Cl (303g 13/06 [58]Field of Search 118/637; 117/17.5;

[56] References Cited UNITED STATES PATENTS 3,455,276 7/1969 Anderson118/637 3,457,900 7/1969 Drexler ll3/637 3,543,720 12/1970 Drexler etal.. 118/637 3,641,969 2/1974 Hakanson 118/637 3,643,629 2/1969 Kangaset al.. 118/637 3,823,688 7/1974 Klett 118/637 OTHER PUBLICATIONS IBMTechnical Disclosure Bulletin; Medley, H. C.; Vol. 2, no. 2, Aug. 1959.

Primary Examiner-Mervin Stein Assistant ExaminerDouglas A. SalserAttorney, Agent, or FirmFrank C. Leach, Jr.

{57] ABSTRACT A magnetic brush roll of an electrostatic reproductionmachine is formed of a non-magnetic core with a resilient polymericmaterial such as polyurethane, for example, on its surface. Thepolyurethane surface is textured to provide a desired roughness, isnon-abrasive, and is abrasion resistant. Carbon is added to thepolyurethane to render it conductive.

10 Claims, 3 Drawing Figures 1 MAGNETIC BRUSH ROLL HAVING RESILIENTPOLYMERIC SURFACE In well-known electrostatic printing processes, asurface bearing a latent electrostatic image is developed by applying adeveloper material comprising toner and a carrier material to thesurface. The small toner particles are held onto the surfaces of therelatively large carrier particles by electrostatic forces, whichdevelop from the contact between the toner and carrier particlesproducing triboelectric charging of the toner and carrier to oppositepolarities. A portion of the applied triboelectrically charged toner isselectively attracted to the image areas of the surface. and theremainder of the developer material is removed and allowed torecirculate to form subsequent images.

In order to assure clear, sharp images. it is necessary that the tonerobtain a high triboelectric charge prior to development. This hasgenerally been effected in prior devices by selecting toner and carriermaterials which are widely separated in the triboelectric series and bycausing agitation and stirring of the developer material prior todevelopment. Further, the ratio of toner to carrier in the developermaterial or mix is closely controlled. However, even when the mostoptimum materials and mixing devices are utilized, the triboelectriccharge of the toner for a given toner-carrier ratio is ofteninsufficient to provide uniform high quality copy output.

Various prior art developing mechanisms incorporate a magnetic brushcomprising a cylindrical member or roll rotatably mounted relative to afixed magnetic field generating means onto which multicomponent magneticdeveloper material is delivered. The magnetic field generating meanscreates a magnetic field causing the magnetic developer to form inbristle-like arrays over the surface of the cylindrical member or rollas it is rotated into contact with an electrostatic latent image-bearingsurface.

For the surface of a magnetic brush roll to transport the magneticdeveloper to an electrostatic latent image-bearing surface, it haspreviously been suggested in U.S. Pat. No. 3,040,704 to Bliss to formthe roll with a roughened external surface. However, attempts to roughenthe surface of the roll, which is formed of a non-magnetic material suchas aluminum, brass, or other soft alloy, by cutting grooves, serrations,or knurls therein have resulted in the surface being rapidly worn downby the abrasive action of the developer material.

It also has been previously suggested in U.S. Pat. No. 3,219,014 to Mottet al to sandblast the surface of a magnetic brush roll to roughen thesurface in a uniform pattern. However, sandblasting does not make thesurface rough enough. Furthermore, the wear of the sandblasted surfaceresults in polished high spots to reduce the transport capability forthe developer material by the sandblasted surface.

Instead of forming the roughened surface directly in the magnetic brushroll by grooves, serrations, knurls, or sandblasting, it has previouslybeen suggested in U.S. Pat. No. 3,246,629 to Shelffo to bond a layer ofirregular shaped particles to the surface of the magnetic brush roll.This provides a random roughened surface.

In transporting the developer material to the electrostatic latentimage-bearing surface, the developer material is moved either uphill ordownhill depending on how the entire machine is arranged. When thedeveloper material is moved uphill. the surface of the magnetic brushroll must be rough enough to enable the carrier particles to not sliderelative thereto while being advanced uphill by the magnetic brush roll.

While the magnetic brush roll of the aforesaid Shelffo patent provides aroughened surface, this surface lacks the desired properties of beingnon-abrasive and resilient. The abrasive surface of the magnetic brushroll of the aforesaid Shelffo patent causes wear on the carrierparticles of the developer material, particularly in the slightclearance area between the magnetic brush roll and the electrostaticlatent image-bearing surface since the abrasive surface causes thecarrier particles to rub against each other and against the surface ofthe magnetic brush roll. Lack of resiliency in the surface of themagnetic brush roll of the aforesaid Shelffo patent pre vents thesurface of the magnetic brush roll from giving to a slight degree when aplurality of the carrier particles are disposed in engagement with eachother between the magnetic brush roll and the electrostatic latentimage-bearing surface with a slightly greater overall distance than theclearance.

The present invention satisfactorily solves the foregoing problems byproviding a roughened surface which is both resilient and non-abrasiveas well as being abrasion resistant. The resilient and non-abrasivesurface of the magnetic brush roll of the present invention in creasesthe life of the carrier particles by reducing wear of the carrierparticles. Thus, wear on the carrier particles is reduced not only bythe non-abrasive surface of the magnetic brush roll of the presentinvention, but its resiliency prevents wear when the carrier particlesare within the clearance area in which they tend to have the greatestrubbing relation with the magnetic brush roll and with each other.

Even though the surface ofthe magnetic brush roll of the presentinvention is both resilient and non-abrasive. it still is rough. As aresult, it provides the desired surface to enable the magnetic brushroll to advance the developer material or mix in an uphill direction sothat the carrier particles, which have the toner particles thereon, areadvanced to the clearance area between the magnetic brush roll and theelectrostatic latent image-bearing surface.

The present invention provides the improved magnetic brush roll throughhaving a resilient polymeric material secured to a non-magnetic core.Because it is necessary to have a bias on the magnetic brush roll. atleast the surface of the resilient polymeric material must beconductive. In its preferred form, the resilient polymeric material ofthe magnetic brush roll of the present invention is homogeneous andconductive throughout.

An object of this invention is to provide a magnetic brush roll having anon-abrasive and resilient surface that is rough or textured.

Another object of this invention is to provide a magnetic brush rollhaving a resilient polymeric material as its surface.

The foregoing and other objects, features, and adv antages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawing.

In the drawing:

FIG. 1 is a schematic sectional view of a portion of an electrostaticreproduction machine having the magnetic brush roll of the presentinvention.

FIG. 2 is a fragmentary perspective view of a portion of one form of themagnetic brush roll of the present invention.

FIG. 3 is a fragmentary sectional view of another form of the magneticbrush roll of the present invention.

Referring to the drawing and particularly FIG. I, there is shown aportion of an electrostatic reproduction machine having a photoconductordrum ll. which functions as the electrostatic latent imagebearingsurface. The photoconductor drum 11 is rotated clockwise by being drivenfrom a main power source.

The developer material, which comprises a mix of carrier particles andtoner particles. is stored in a sump portion 14 of a magnetic brushdeveloper station 15. The toner particles are supplied to the sumpportion 14 from a toner cartridge (not shown) by a metering cylin der(not shown) of a replenisher (not shown), which has an agitator (notshown). through an opening 16 in the magnetic brush developer station tothe sump portion 14 of the magnetic brush developer station 15. Counterrotating augers l7 and i8 stir the freshly added toner with thedeveloper material in the sump portion 14 to assure complete mixingthereof as well as to enhance the triboelectric charging of thedeveloper material.

The developer material is metered from the sump portion 14 to atransport portion 19 of the magnetic brush developer station 15 by ametering gate 20. The transport portion 19 of the magnetic brushdeveloper station 15 has a transport roll 2i disposed therein beneath amagnetic brush roll 22.

The transport roll 21, which rotates at a speed less than the rotationalspeed of the magnetic brush roll 22 to provide a surface velocity of thetransport roll 2] no greater than the surface velocity of the magneticbrush roll 22, rotates clockwise while the magnetic brush roll 22rotates counterclockwise. The transport roll 2] surrounds a fixed drum23 which has magnets 24 on a portion of the surface thereof to aid inholding the deveL oper material on the transport roll 21 until thedeveloper material is advanced to a position adjacent the oppositelyrotating magnetic brush roll 22.

As the developer material is advanced by the transport roll 21 to themagnetic brush roll 22, the developer material is attracted to themagnetic brush roll 22 by magnets 25. which are fixed and disposedwithin the magnetic brush roll 22. The magnets 25 may be of any suitabletype as long as they cause the developer material to adhere to themagnetic brush roll 22 and have a bristle-like array adjacent thephotoconductor I].

As shown in FIG. 2, the magnetic brush roll 22 includes a core 26 of anon-magnetic material such as aluminum. for example. The core 26 isclosed at its ends by plates 27.

A shaft 28 extends from the plate 27 at one end of the core 26 and isdriven from a main power source by a chain passing around a sprocket onthe shaft 28. The transport roll 21 is driven in unison with themagnetic brush roll 22 through the same chain cooperating with a shaft29 of the transport roll 21. The other plate 27 is rotatably supportedby a bearing on a fixed shaft 30 (see FIG. I) on which the magnets 25are supported.

The core 26 of the magnetic brush roll has a sleeve 3] of a resilientpolymeric material secured thereto. The sleeve 31 has its surfacetextured so as to be roughened to a desired extent. The roughnesspattern in the sleeve 31 can be uniform or non-uniform.

One suitable example of the resilient polymeric material of the sleeve31 is polyurethane. The sleeve 3| is homogeneous and is conductive sothat a desired bias can be applied to the magnetic brush roll 22. Whilepolyurethane is not conductive. carbon is added thereto to insure thatthe sleeve 3] is conductive.

One means of forming the sleeve 3| is to use Norton Company's AH299grinding tube as a mold. The tube is machined to an outer diameter of2.4 inches and then grit blasted to produce a random. textured surfaceon the tube as the mold. Then. DuPont 958-202 steel blue Teflon releasecoat is applied to the surface of the mold.

The mold is then dip coated twelve times within a conductivepolyurethane solution with the mold being inverted after each of thedips. The conductive polyurethane solution is prepared by adding onehundred parts by weight of Hughson Chemical Company's TS- l525 37urethane lacquer resin. 8.3 parts by weight of Cabot Corporations VulcanXC-72 conductive carbon black, parts by weight of toluene, and 100 partsby weight of isopropyl alcohol within an attritor and running theattritor at full speed for l hour.

After each coating of the conductive polyurethane solution is formed onthe mold. it is air dryed for at least l5 minutes before an additionalcoat is applied by dipping. After every fourth dip and after air drying,the mold is placed in an air circulating oven and allowed to dry for atleast 15 minutes at F to remove any residual solvent.

This forms the sleeve 31, which is removed from the mold. After turningthe sleeve 31 inside out. the sleeve 31 is deposited over the core 26.which has been adhesive coated by spray coating with EC2290 modifiedepoxy adhesive of 3M and completely dried. The sleeve 31 is expanded byair to be able to fit over the core 26. After the sleeve 31 has beendisposed over the core 26. it is cured for one hour at 300 F.

Tests have indicated that the tensile strength of the sleeve 3] is 4,000p.s.i. with an ultimate elongation in excess of 800 per cent. The tearstrength of the sleeve 31 is 330 pounds per inch thickness, and it has ahardness of 65 on a shore A durometer. Its volume resistivity is 10ohm-cm.

Accordingly, the magnetic brush roll 22 has a surface. which is rough ortextured. non-abrasive, and abrasion resistant. At the same time, thesleeve 3i is resilient and is conductive throughout. This permits therequired bias to be applied to the magnetic brush roll 22.

As the magnetic brush roll 22 advances the developer material toward thephotoconductor drum I i. it passes a bead control device 32. The beadcontrol device 32 limits the thickness of the developer material on themagnetic brush roll 22 prior to being advanced into the positionadjacent the photoconductor drum H.

The magnetic brush developer station 15 supports a pile fabric seal 33,which is made of a material such as Kodel. for example. The purpose ofthe seal 33, which engages the photoconductor drum H. is to prevent atoner cloud from escaping from the magnetic brush developer station 15.

After the magnetic brush roll 22 has advanced the developer materialpast the photoconductor drum 11, the developer material remaining on themagnetic brush roll 22 is released after passing the last of the magnets25 and returned to the sump portion 14 of the magnetic brush developerstation l5.

The magnetic brush developer station l5 also sup ports a blade scraper34, which is conductive coated Mylar, adjacent the photoconductor drum Hand spaced slightly therefrom. The purpose of the blade scraper 34 is tokeep the toner and carrier particles from escaping from the magneticbrush developer station 15.

A seal 35, which is spaced slightly from the photoconductor drum 11,also is supported by the magnetic brush developer station l5 and ispassed by the photoconductor drum ll after the photoconductor drum llmoves past the scraper 34. The seal 35, which also is conductive coatedMylar, likewise functions to keep the toner and carrier particles fromescaping from the magnetic brush developer station 15.

Instead of the magnetic brush roll 22 having the sleeve 31, which ishomogeneous polyurethane with carbon, a magnetic brush roll 37 (see FIG.3) could be employed in which the core 26 would again be used. The core26 would have a layer 38 of polyurethane without carbon thereon so thatthe layer 38 would not be conductive. Then, a layer 39 of polyurethanewith carbon could be applied to the layer 38 by being painted thereon.The layer 39 would need to be only about 0.00l inch thick.

Thus, the magnetic brush roll 37 would be conductive only along itssurface. However, this is sufficient to provide the desired biasthereon.

The sleeve 3] of the magnetic brush roll 22 or the layer 38 of themagnetic brush roll 37 must be at least 0.010 inch thick and ispreferably at least 0.015 inch thick. While the sleeve 31 of themagnetic brush roll 22 or the layer 39 of the magnetic brush roll 37 hasa hardness of 65 on a Shore A durometer, it should be understood thateither could have a hardness up to 95 on a Shore A durometer and stillhave sufficient resiliency.

While the resilient polymeric material has been described as beingpolyurethane, it should be understood that any other resilient polymericmaterial having the desired properties could be employed. This includesthe capability of having a conductive material such as carbon, forexample, added without the material losing its other desired propertiesof being resilient, nonabrasive. and abrasion resistant. Thus, anysynthetic rubber having the properties of being resilient, nonabrasive.and abrasion resistant could be utilized, for example. The rubber couldbe dip-coated on a textured core of a non-magnetic material, forexample, to have the desired roughness. it is necessary that anyresilient polymeric material be non-abrasive and abrasion resistant aswell as having a sufficient roughness to permit the developer materialto have a foothold on the magnetic brush roll.

While the roughness of the material can be within varying ranges, it ispreferred that the roughness be no greater than that produced by amolding from a 50 grit sandpaper. The roughness preferably is no lessthan that produced by ninety grit sandpaper.

While the sleeve 3! has been described as being formed through a dippingprocess on a mold and then removing the sleeve 31 for application on thecore 26,

it should be understood that any other suitable process could beemployed. For example. the material could be injection molded around acore or a sleeve could be extruded with the material having to bethermoplastic in nature to allow the desired roughness to be embossed inits surface.

While the present invention has been shown and described as having thedeveloper material moved uphill by the magnetic brush roll, it should heunderstood that the magnetic brush roll of the present invention couldbe utilized where the developer material is moved downhill. This wouldbe particularly useful in a relatively high speed machine.

An advantage of this invention is that it reduces the wear of thedeveloper material. Another advantage of this invention is that it isparticularly useful in moving a material uphill to an electrostaticlatent imagebearing surface.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is:

1. ln an electrophotographic development apparatus of the magnetic brushtype having:

a surface on which a latent image is formed;

a rotatably mounted hollow roll including a core of non-magneticmaterial and a resilient polymeric material secured to said core to formthe surface of said roll;

said resilient polymeric material having at least its surfaceelectrically conductive;

said resilient polymeric material having its surface non-abrasive,abrasion resistant, and rough;

magnetic means disposed within said core for creating a magnetic fieldin the path of the periphery of said roll;

and means to bring a developer material into contact with the surface ofsaid resilient polymeric material of said roll. said roll being disposedadjacent said surface on which the latent image is formed so that saidroll can transport the developer material in a brush-like configurationto the surface on which the latent image is formed.

2. The apparatus according to claim 1 in which said resilient polymericmaterial of said roll is electrically conductive throughout itsentirety.

3. The apparatus according to claim 2 in which said resilient polymericmaterial comprises a single homo geneous layer on said core.

4. The apparatus according to claim 3 in which said resilient polymericmaterial has a hardness no greater than on a Shore A durometer.

5. The apparatus according to claim 4 in which said layer of resilientpolymeric material is at least 0.010 inch thick.

6. The apparatus according to claim 5 in which said layer of resilientpolymeric material is polyurethane having an electrically conductivematerial dispersed throughout.

7. The apparatus according to claim 2 in which said resilient polymericmaterial comprises:

a first homogeneous layer secured to said core;

and a second layer secured to said first layer. said second layer beingelectrically conductive.

8. The apparatus according to claim 7 in which:

said resilient polymeric material is polyurethane;

and said second layer includes an electrically conductive material insaid polyurethane.

9. The apparatus according to claim 8 in which said

1. IN AN ELECTROPHOTOGRAPHIC DEVELOPMENT APPRATRUS OF THE MAGNETIC BRUSHTYPE HAVING: A SURFACE ON WHICH A LATENT IMAGE IS FORMED; A ROTATABLYMOUNTED HOLLOW ROLL INCLUDNG A CORE OF NONMAGNETIC MATERIAL AND ARESILIENT POLYMERIC MATERIAL SECURED TO SAID CORE TO FORM THE SURFACE OFSAID ROLL; SAID RESILIENT POLYMERIC MATERIAL HAVING AT LEAST ITS SURFACEELECTRICALLY CONDUCTIVE; SAID RESILIENT POLYMERIC MATERIAL HAVING ITSSURFACE NONABRASIVE, ABRASION RESISTANT, AND ROUGH; MAGNETIC MEANSDISPOSED WITHIN SAID CORE FOR CREATING A MAGNETIC FIELD IN THE PATH OFTHE PERIPHERY OF SAID ROLL; AND MEANS TO BRING A DEVELOPER MATERIAL INTOCONTACT WITH THE SURFACE OF SAID RESILIENT POLYMERIC MATERIAL OF SAIDROOL, SAID ROLL BEING DISPOSED ADJACENT SAID SURFACE ON WHICH THE LATENTIMAGE IS FORMED SO THAT SAID ROLL CAN TRANSPORT THE DEVELOPER MATERIALIN A BRUSH-LIKE CONFIGURATION TO THE SURFACE ON WHICH THE LATENT IMAGEIS FORMED.
 2. The apparatus according to claim 1 in which said resilientpolymeric material of said roll is electrically conductive throughoutits entirety.
 3. The apparatus according to claim 2 in which saidresilient polymeric material comprises a single homogeneous layer onsaid core.
 4. The apparatus according to claim 3 in which said resilientpolymeric material has a hardness no greater than 95 on a Shore Adurometer.
 5. The apparatus according to claim 4 in which said layer ofresilient polymeric material is at least 0.010 inch thick.
 6. Theapparatus according to claim 5 in which said layer of resilientpolymeric material is polyurethane having an electrically conductivematerial dispersed throughout.
 7. The apparatus according to claim 2 inwhich said resilient polymeric material comprises: a first homogeneouslayer secured to said core; and a second layer secured to said firstlayer, said second layer being electrically conductive.
 8. The apparatusaccording to claim 7 in which: said resilient polymeric material ispolyurethane; and said second layer includes an electrically conductivematerial in said polyurethane.
 9. The apparatus according to claim 8 inwhich said resilient polymeric material has a hardness no greater than95 on a Shore A durometer.
 10. The apparatus according to claim 1 inwhich said resilient polymeric material is polyurethane.